The mechanism of biogenesis and assembly of the lac permease of E. coli will be pursued testing the notion that the permease is synthesized in a soluble precursor form. First, detailed pulse-chase kinetics will be performed to establish the relationship, in time, between the observed soluble and membrane components. Second, the relationship of these components to other lac gene products will be determined using specific antibody precipitation and SDS-PAGE. Finally, purification of the putative precursors and products will be performed and the relationship between these components will be examined by peptide fingerprinting and antibody cross reactivity. In addition, genetic studies will be pursued in order to characterize other mutants which appear to be defective in lac permease biogenesis and transport functions.